/*
 *  This file is part of the Jikes RVM project (http://jikesrvm.org).
 *
 *  This file is licensed to You under the Eclipse Public License (EPL);
 *  You may not use this file except in compliance with the License. You
 *  may obtain a copy of the License at
 *
 *      http://www.opensource.org/licenses/eclipse-1.0.php
 *
 *  See the COPYRIGHT.txt file distributed with this work for information
 *  regarding copyright ownership.
 */
package org.mmtk.plan;

import org.mmtk.utility.Log;
import org.mmtk.utility.options.Options;
import org.mmtk.vm.VM;
import org.vmmagic.pragma.*;
import org.vmmagic.unboxed.*;

/**
 * This abstract class is the fundamental mechanism for performing a
 * transitive closure over an object graph.<p>
 *
 * Some mechanisms only operate on nodes or edges, but due to limitations
 * of inheritance we have combined these two here.
 *
 * @see org.mmtk.plan.TraceLocal
 */
@Uninterruptible
public abstract class TransitiveClosure {

  /** Database of specialized scan classes. */
  private static final Class<?>[] specializedScans = new Class[VM.activePlan.constraints().numSpecializedScans()];

  /**
   * A transitive closure has been created that is designed to work with a specialized scan method. We must
   * register it here so the specializer can return the class when queried.
   *
   * @param id The method id to register.
   * @param specializedScanClass The class to register.
   */
  @Interruptible
  public static synchronized void registerSpecializedScan(int id, Class<?> specializedScanClass) {
	  //kathy
	  if (Options.scaleDebug != null && Options.scaleDebug.getValue() > 7) {
		  Log.write("registerSpecializedScan, id=");Log.write(id);
		  Log.write("class=");Log.writeln(specializedScanClass.getName());
		  Log.flush();
	  }
    specializedScans[id] = specializedScanClass;
  }

  /**
   * Get the specialized scan with the given id.
   */
  public static Class<?> getSpecializedScanClass(int id) {
    if (VM.VERIFY_ASSERTIONS) VM.assertions._assert(specializedScans[id] != null);
    return specializedScans[id];
  }

  /** The specialized scan identifier */
  protected final int specializedScan;

  /**
   * Constructor
   */
  protected TransitiveClosure() {
    this(-1);
  }

  /**
	 * Constructor
	 * 
	 * @param specializedScan
	 *            The specialized scan for this trace.
	 */
	protected TransitiveClosure(int specializedScan) {
		this.specializedScan = specializedScan;
		Log.prependThreadId();
		if (specializedScan >= 0) {
			if (VM.VERIFY_ASSERTIONS) {
				//Kathy
				if (Options.scaleDebug != null && Options.scaleDebug.getValue() > 7) {
					Log.write("\tTransitiveClosure entered with getClass()=");
					Log.write(getClass().getName());
					Log.write(", getSpecializedScanClass(");
					Log.write(specializedScan);
					Log.write(")=");
					Log.writeln(getSpecializedScanClass(specializedScan).getName());
					Log.flush();
				}
				VM.assertions._assert(getClass() == getSpecializedScanClass(specializedScan));
			}
		}
	}

  /**
   * Trace an edge during GC.
   *
   * @param source The source of the reference.
   * @param slot The location containing the object reference.
   */
  public void processEdge(ObjectReference source, Address slot) {
    VM.assertions.fail("processEdge not implemented.");
  }

  /**
   * Trace a node during GC.
   *
   * @param object The object to be processed.
   */
  public void processNode(ObjectReference object) {
    VM.assertions.fail("processNode not implemented.");
  }
}
